Agriculture Reference
In-Depth Information
10 November as 'Date 5'. In the first step, the
stems were separated with a decortication
unit and, in the second step, with a coarse
separator. A detailed description is given by
Müssig and Martens (2003). After separation,
the tensile strength of the fibre bundles was
determined by testing collectives with the
Stelometer device (for a description, see the
section on collective strength/Stelometer);
the results are presented in Fig. 10.2. In 1996
and 1997, the progress of retting was very
smooth and the stems could be baled and
stored without any problems. As far as
strength values were concerned, no damage
to the samples could be found after 1 month
of retting. The extreme decrease of strength
observed later in 1998 was related to the high
amount of precipitation during the first days
of October. In 1998, a high amount of pre-
cipitation occurred after cutting the stems.
After constant retting in the beginning, the
water and temperature conditions changed
after testing Date 3. Wet conditions led to
high microorganism activity, which damaged
the fibres.
With a view to producing high-quality
hemp fibres for industry, it is important to con-
trol the strength and fineness of the fibres
along the whole production chain. The effect
of crop management decisions such as cultivar
choice, sowing date, plant density and
harvesting date on these parameters is
important. To achieve good fibre properties,
quality management must start with cultivation,
harvesting, harvest date and, last but not least,
the retting process and duration. Considering
all these issues, hemp (
Cannabis sativa
L
.
) can
be a profitable crop with the right profile to fit
into sustainable farming systems (Müssig and
Martens, 2003).
Internal quality systems have been devel-
oped by fibre suppliers to ensure the origin and
quality of the raw material. In recent years,
adapted or new testing methods for bast and
leaf fibres have been developed. While interna-
tional standards for testing bast fibres are avail-
able for the textile industry (ISO 2370:1980
Textiles - Determination of Fineness of Flax
Fibres - Permeametric methods, ASTM
D6961-03 Test Method for Color Measurement
of Flax Fibre and ASTM D7025-04 Test
Method for Assessing Clean Flax Fibre
Fineness), there are no international standards
for the testing of natural fibres for technical
applications like reinforced plastics. Various
authors have presented the properties of sev-
eral natural fibres and have collected the results
of numerous investigations (Hearle and Peters
1963; Haudek and Viti, 1980; Batra, 1998).
But, the comparison of more than one fibre
140
120
100
HempFlax 1996
80
HempFlax 1997
HempFlax 1998
60
40
Mean value
Standard deviation
20
0
Fig. 10.2.
Influence of retting duration on collective strength (Stelometer) (Müssig and Harig, 2000).
